[Bug c++/86557] New: missed vectorization with std::vector compared to icc 18

[nightstrike at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86557

            Bug ID: 86557
           Summary: missed vectorization with std::vector compared to icc
                    18
           Product: gcc
           Version: 8.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nightstrike at gmail dot com
  Target Milestone: ---

ICC 18 is able to vectorize this loop, while GCC 8 is not.

#include <vector>

std::size_t f(std::vector<std::vector<float>> const & v) {
    std::size_t ret = 0;
    for (std::size_t i = 0; i < v.size(); ++i)
      ret += v[i].size();
    return ret;
}